The present invention relates to a micro-bubble generating system for efficiently dissolving gas such as the air, oxygen gas, etc. into liquid such as city water, river water, etc., for purifying polluted water and for effectively utilizing the water for reconditioning and renewal of water environment.
In conventional type aeration systems, e.g. in most of aeration systems using micro-bubble generating system installed for culture and growth of aquatic animals, air bubbles are generated by injecting the air under pressure into water through fine pores of tubular or planar micro-bubble generating system installed in the tank, or air bubbles are generated by introducing the air into water flow with shearing force or by vaporizing the air dissolved in water by rapidly reducing pressure of the pressurized water.
In the aeration process using the micro-bubble generating system with the above functions, operation is basically controlled by adjusting the air supply quantity or the number of the micro-bubble generating systems to be installed, while it is necessary to efficiently dissolve gas such as air, carbon dioxide, etc. into water and further to promote circulation of the water.
However, in the aeration system using the conventional type micro-bubble generating system, e.g. diffusion system based on injection, even when fine pores are provided, when air bubbles are injected under pressure through pores, volume of each of the air bubbles is expanded, and diameter of each air bubble is increased to several millimeters due to surface tension of the air bubbles during injection. Thus, it is difficult to generate air bubbles of smaller diameter. Also, there are problems such as clogging of the pores or increase of power consumption caused by the operation for long time.
In the system to generate the air bubbles by introducing the air into water flow with shearing force using vanes and air bubble jet stream, it is necessary to have higher number of revolutions to generate cavitation. Also, there are problems of power consumption increase and the problem of corrosion of vanes or vibration caused by generation of cavitation. Further, there are problems in that only a small amount of micro-bubbles can be generated.
In the system where gas-liquid two-phase flow collides with the moving vane or projection, fishes or small aquatic animals in natural lakes or culture tanks may be injured, and this causes trouble in the development and maintenance of the environmental condition necessary for the growth of fishes and other aquatic animals.
Further, in the pressurizing system, the system must be designed in larger size and requires higher cost, and operation cost is also high.
In none of the prior art in this field as described above, it has been possible to generate micro-bubbles with diameter of not more than 20 xcexcm in industrial scale.
After fervent study efforts, the present inventors have successfully developed the present invention, by which it is possible to generate micro-bubbles with diameter of not more than 20 xcexcm in industrial scale.
As shown in FIG. 12, which indicates the principle of the system according to the present invention, a micro-bubble generating system is provided, which comprises a conical space 100 in a container, a pressure liquid inlet 500 provided in tangential direction on a part of circumferential surface of inner wall of the space, a gas introducing hole 80 opened at the center of the bottom 300 of the conical space, and a swirling gas-liquid outlet 101 near the top of the conical space.
The entire system or at least the swirling gas-liquid outlet 101 is submerged in the liquid, and by sending pressure liquid from the pressure liquid inlet 500 into the conical space 100, a swirling flow is formed inside, and negative pressure is generated along the axis of the conical tube. By this negative pressure, the gas is sucked through the gas introducing hole 80. As the gas passes along the axis of the tube where the pressure is at the lowest, a narrow swirling gas cavity 60 is generated.
In the conical space 100, a swirling flow is generated from the inlet (pressure liquid inlet) 500 toward the outlet (swirling gas-liquid outlet) 101. As cross-sectional area of the space 100 is gradually reduced toward the swirling gas-liquid outlet 101, both the swirling velocity and velocity of the flow directed toward the outlet are increased at the same time.
In association with this swirling, centrifugal force is applied on the liquid and centripetal force is applied on the air at the same time because of the difference of specific gravity between the liquid and the gas. As a result, the liquid portion and the gas portion become separable from each other, and the gas is turned to a narrow thread-like gas swirling cavity 60, which is narrowed down and runs continuously up to the outlet 101 and is then injected through the outlet. At the same time as the injection, swirling is rapidly weakened by the surrounding stationary water. Then, radical difference in swirling velocity occurs before and after that point. Because of the difference of swirling velocity, the thread-like gas cavity 60 is cut off in continuous and stable manner. As a result, a large amount of micro-bubbles, e.g. micro-bubbles of 10 to 20 xcexcm in diameter, are generated near the outlet 101 and are discharged.
Specifically, the present invention provides:
(1) a swirling type micro-bubble generating system, comprising a container main unit having a conical space, a pressure liquid inlet provided in tangential direction on a part of circumferential surface on inner wall of the space, a gas introducing hole opened on the bottom of the conical space, and a swirling gas-liquid outlet arranged at the top of the conical space;
(2) a swirling type micro-bubble generating system, comprising a container main unit having a truncated conical space, a pressure liquid inlet provided in tangential direction on a part of circumferential surface on inner wall of the space, a gas introducing hole opened on the bottom of the truncated conical space, and a swirling gas-liquid outlet arranged in the upper portion of the truncated conical space;
(3) a swirling type micro-bubble generating system, comprising a container main unit having a space of bottle-like shape, a pressure liquid inlet provided in tangential direction on a part of circumferential surface on inner wall of the space, a gas introducing hole opened on the bottom of the bottle-like space, and a swirling gas-liquid outlet arranged at the top of the bottle-like space;
(4) a swirling type micro-bubble generating system according to one of (1) to (3) above, wherein a plurality of pressure liquid inlets are provided with spacings in tangential direction on a part of circumferential surface having the same radius of curvature on inner wall of the space;
(5) a swirling type micro-bubble generating system according to one of (1) to (4) above, wherein a plurality of pressure liquid inlets are provided with spacings in tangential direction on a part of circumferential surface having different radii of curvature on inner wall of the space;
(6) a swirling type micro-bubble generating system according to one of (1) to (5) above, wherein the pressure liquid inlet is provided on a part of circumferential surface of inner wall near the bottom of the space;
(7) a swirling type micro-bubble generating system according to one of (1) to (6) above, wherein the pressure liquid inlet is provided on a part of circumferential surface of inner wall near a point halfway down of the space; and
(8) a swirling type micro-bubble generating system according to one of (1) to (7) above, wherein a baffle plate is arranged downstream of the swirling gas-liquid outlet.
In the other aspects, the present invention further provides:
(9) a swirling type micro-bubble generating system, comprising a liquid flow swirling introducing structure of a circular accommodation chamber on a lower flow base, a swirling ascending liquid flow forming structure formed on inner peripheral portion of a covered cylinder with diameter gradually increased in upward direction, a swirling descending liquid flow forming structure formed inside the peripheral portion, a swirling cavity under negative pressure formed at the center of said covered cylinder by separating action of centrifugal and centripetal forces of the swirling ascending liquid flow and the swirling descending liquid flow, a gas vortex flow forming structure where a swirling and descending gas vortex flow is formed as gas self-sucked from gas self-sucking pipe mounted at the center of upper cover and gas components eluted from the swirling water flow are accumulated, said gas vortex flow being extended and narrowed down, a micro-bubble generating structure for generating micro-bubbles as gas vortex flow is forcibly cut off when the extended and narrowed gas vortex flow enters the central reflux port at the bottom of the circular accommodation chamber, swirling velocity decreased due to resistance of the discharge passage, thereby causing difference in swirling velocity, and a swirling injection flow discharge structure for discharging liquid flow through a lateral discharge port as swirling injection flow including the generated micro-bubbles in the swirling descending liquid flow;
(10) a swirling micro-bubble generating system, wherein there is provided a liquid flow swirling introducing structure in the circular accommodation chamber, a circular accommodation chamber is provided on upper portion of the lower flow base, a liquid flow inlet is opened in tangential direction with respect to inner peripheral surface from lateral direction on said circular accommodation chamber, and a pump is connected to introduce water flow forcibly and swirling;
(11) a swirling type micro-bubble generating system, wherein there is provided a dual swirling liquid flow forming structure of the swirling ascending liquid flow and the swirling descending liquid flow in the covered cylinder with its diameter gradually increased in upward direction, a covered cylinder with diameter gradually increased in upward direction is erected vertically on upper portion of said circular accommodation chamber, the swirling introducing flow of the circular accommodation chamber is introduced, a swirling ascending liquid flow is formed by swirling and ascending along the peripheral portion in the covered cylinder, when the swirling ascending liquid flow reaches the upper limit, it is sent back to inner portion from peripheral portion to swirl and descend, thus forming a swirling descending liquid flow;
(12) a swirling type micro-bubble generating system, wherein there is provided a gas vortex flow forming structure, a swirling cavity under negative pressure is formed at the central portion by centrifugal and centripetal forces of dual swirling flow of the swirling ascending liquid flow and the swirling descending liquid flow inside the covered cylinder with diameter gradually increased in upward direction, self-sucking gas and gas components eluted from said swirling flow are accumulated in said swirling cavity under negative pressure, and swirling descending gas flow is formed while being extended and narrowed down;
(13) a swirling type micro-bubble generating system, wherein said system comprises a micro-bubble generating structure, and a central reflux port is provided at the bottom center of said circular accommodation chamber, a discharge passage is provided from said reflux port to a lateral discharge port of said flow base, and when the gas vortex flow swirling and descending while being extended and narrowed down in the central portion inside the covered cylinder enters and flows out of the central reflux port, the gas vortex flow undergoes resistance from the discharge passage and the swirling velocity is decreased, thereby causing swirling velocity difference between upper and lower portions of the vortex flow, the vortex flow is forcibly cut off due to the velocity difference, and micro-bubbles are generated;
(14) a swirling type micro-bubble generating system, wherein said system comprises a micro-bubble generating structure, a plurality of lateral discharge ports are formed in radial direction on the central reflux port, the gas vortex flow swirling and descending through the central portion of said covered cylinder is sent through the central reflux port toward said plurality of lateral discharge ports in the order of the swirling direction, resistance from the passage caused by the flow into the lateral discharge ports and resistance from the passage due to collision against side wall of the reflux port are repeatedly and alternatively applied for a plurality of times, swirling velocity difference is generated between upper and lower portions of the vortex flow each time the flow undergoes the resistance, and the vortex flow is cut off, and micro-bubbles are generated;
(15) a swirling type micro-bubble generating system, wherein a connection pipe for discharge as provided on the lateral discharge port of said flow base is bent and protruded in such manner as to follow the swirling flow forming direction in said covered cylinder; and
(16) a method for swirling type micro-bubble generation, using a micro-bubble generating system, which comprises a container main unit having a conical space, a pressure liquid introducing port opened in tangential direction on a part of circumferential surface of inner wall of said space, a gas introducing hole opened at the bottom of said conical space, and a swirling gas-liquid discharge outlet opened at the top of said conical space, whereby said method comprises a first step of forming a gas vortex flow swirling and flowing while being extended and narrowed down in said conical space, and a second step of generating micro-bubbles when the gas vortex flow is forcibly cut off due to the difference of swirling velocity between front portion and rear portion of the gas vortex flow.